Method and apparatus for improving the separation efficiency of a cyclone separator intended for gaseous fluid flows

ABSTRACT

A method and apparatus for improving the separation efficiency of a cyclone separator intended for gaseous medium flows in which an incoming gaseous medium flow to be cleansed is directed into the cyclone separator through an inlet duct such that the incoming medium flow ends up in a downward, revolving flow movement inside the cyclone separator until the incoming medium flow reaches a bottom end of a conical lower part of the cyclone separator, and then becomes a revolving tornado flow that flows in a generally upward direction opposite to the direction of the downward, revolving flow movement. An outlet flow of cleansed gaseous medium is directed through a center pipe situated in the cyclone separator. A component-flow pipe is arranged in the center pipe such that the component-flow pipe has an inlet opening in a wall of the center pipe. A component flow of the incoming medium flow is passed from a location within the cyclone separator through the inlet opening in the wall of the center pipe into the component-flow pipe directed out of the component-flow pipe against the tornado flow such that the component flow disintegrates the tornado flow and thereby prevents solid matter from being carried along with the tornado flow through the center pipe into the outlet flow of the cleansed medium flow.

FIELD OF THE INVENTION

The invention concerns a method for improving the separation efficiencyof a cyclone separator intended for gaseous medium flows, in whichcyclone separator the gaseous medium flow to be cleansed flows into thecyclone separator through an inlet duct and ends up in a revolving flowmovement inside the cyclone separator, which movement is changed, in thebottom end of the conical lower part of the cyclone separator, into arevolving tornado flow that flows in the opposite direction.

BACKGROUND OF THE INVENTION

In the prior art, cyclone separators are used for separation ofparticles of solid matter present in gas flows. In a cyclone separator,the gaseous medium flow enters inside the cyclone separator into acentrifugal flow which revolves inside the cyclone, as a rule, flowingfrom the top towards the bottom. When the cyclone operates in thevertical position, the inlet of the gaseous medium flow is placed at thetop edge of the cyclone separator, in which case the gaseous medium flowthat flows in starts revolving downwards inside the cylindrical cycloneseparator. When the revolving medium flow flows down into the conicalbottom portion of the cyclone separator while maintaining its flowvelocity, the revolving medium flow is accelerated at a certain angularvelocity. When the revolving medium flow reaches the bottom of theconical bottom portion of the cyclone separator, the revolving mediumflow is forced to turn upwards while maintaining its sense of rotation.Then, as is well known, at the lowest point in the bottom end of thecyclone separator, a so-called tornado effect is produced, which isseen, for example, in summer in wind whirls.

Frequently, dust and other solid matter is absorbed into such tornadowhirls, being carried along by the tornado whirl and raised even to ahigh altitude. It is only after disintegration of the tornado whirl thatthe solid matter can fall down freely and be separated from the tornadoto the environment.

In principle, the same also takes place in a cyclone separator regardingthe tornado formed inside the conical part at the lower end. The tornadovortex always carries along with it some of the dust or particles ofsolid matter entering into the cyclone along with the gaseous mediumflow. This is why cyclone separators can, as a rule, not be consideredto be very good dust separators, because, along with the tornado flow,even large dust particles can flow out of a cyclone separator, for whichreason, by means of the prior-art cyclone separators, a particularlyprecise separation limit cannot be achieved.

At present, a number of different cyclone solutions are used, of whichso-called low-pressure, medium-pressure, and high-pressure cyclonesshould be mentioned. This refers to the pressure loss in the gaseousmedium flowing in the cyclone separator that is required by theflowing-through with a nominal volume. Low-pressure cyclones usuallyhave rather large diameters. On the other hand, the diameters ofhigh-pressure cyclones are relatively small. In high-pressure cyclones,the pressure loss may be up to 2000 Pa, whereas in low-pressure cyclonesthe pressure loss is usually less than 1000 Pa. High-pressure cyclonesare often constructed side by side as groups, in which case such asolution is called a multi-cyclone battery. Such a multi-cyclone batteryis relatively difficult to manufacture, because it comprises a number ofsmall cyclones, whose dimensional accuracy must be very high. This iswhy the manufacture of multi-cyclone batteries is relatively expensive.Also, owing to the magnitude of the pressure loss, their operationrequires considerably more energy than the operation of low-pressurecyclones does.

The efficiency of separation of cyclone separators depends on thecentrifugal field formed inside the cyclone separator. It is commonlyknown that the higher the angular velocity of the gaseous medium flow,the more intensive is the centrifugal field, and that the intensity ofthe centrifugal field is directly proportional to the second power ofthe angular velocity of the medium flow. This is why small-diametercyclone separators are more efficient separators than cyclone separatorsof larger diameter. It also comes from this that, in practicalsolutions, multi-cyclones are adopted more and more frequently eventhough their investment cost and power consumption are higher. In spiteof this, cyclone separators are not capable of meeting the requirementsof good efficiency of separation.

From the prior art, a solution is known by whose means the tornadoeffect can be eliminated to a reasonable extent. This solution consistsof a tornado elimination plate placed at a suitable distance from theorifice of the centre pipe of the cyclone separator, which plateprevents direct flow of the tornado flow into the centre pipe. Adrawback of this prior-art solution is intensive wear of the eliminationplate, and further, the size of the elimination plate may produce unduewear of the cylinder part of the cyclone separator.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention to provide an improvement over theprior-art solutions of cyclone separators. It is a more specific objectof the invention to provide a method that permits a considerableimprovement of the separation efficiency of a cyclone separator.

The method in accordance with the invention is characterized in that,from the incoming medium flow, a component flow is taken, which ispassed through a component-flow pipe, which pipe passes through thecentre pipe of the cyclone separator, against the tornado flow that hasbeen formed, whereby the component flow disintegrates the tornado flowand thereby prevents solid matter from being carried along with thetornado flow, through the centre pipe, into the outlet flow of thecleansed medium flow.

Owing to the solution of the present invention, it is possible toeliminate the access of the contents of dust or solid matter containedin a tornado flow into the centre pipe of a cyclone separator and fromthere further to the outlet flow. By means of the method in accordancewith the invention, with a large-diameter cyclone separator, a degree ofseparation is achieved which equals or even exceeds the efficiency ofseparation of multi-cyclones, but, nevertheless, the gas flow flowingthrough the cyclone separator does not have to form a pressure loss inexcess of 1000 Pa.

The invention is based on the idea that the tornado that has been formedin the conical part of the cyclone separator is disintegrated by meansof a component flow that flows against the tornado, which component flowis preferably taken, or which is absorbed by itself, from the intakeflow of the cyclone separator. Then, the detrimental tornado flow isrecirculated among the incoming gaseous medium flow to be cleansed. Thecomponent flow is passed preferably by means of a component-flow pipewhich passes through the centre pipe of the cyclone and which issubstantially smaller than the diameter of the centre pipe. Theabsorption of the component flow into this component-flow pipe arisesfrom the differences in pressure present in the cyclone separator, theformation of vacuum arising from the high-velocity movement of rotationof the tornado flow present in the conical bottom portion of the cycloneseparator. Owing to the solution in accordance with the invention, thesolid matter present in the tornado flow is recirculated to separation,and thereby the overall capacity of separation of the cyclone separatoris improved considerably, being equal to the overall capacity ofseparation of multi-cyclones.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be described in detail with reference to the solutionof principle of the invention illustrated in the figure in theaccompanying drawing, the invention being, however, not supposed to beconfined to said solution alone.

The figure in the drawing is a schematic sectional view of a preferredembodiment of a cyclone separator that is used in the method inaccordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The cyclone separator that is shown in the figure in the drawing isdenoted generally with the reference numeral 10. The cyclone separator10 comprises a frame part, i.e. a cylindrical mantle part 11, an inletflow duct 12 for the gaseous medium flow A to be cleansed, and a centrepipe 13, through which the cleansed gaseous medium flow flows out as theflow C. The frame part 11 of the cyclone separator 10 is conical at itsbottom portion 14. At the bottom of the conical bottom portion 14, thereis an outlet opening, which is provided with a closing device 15,through which the solid matter is removed as the flow B. Such a solutionis conventional and known from the prior art, and constitutes no part ofthe present invention as yet.

The incoming medium flow A starts revolving inside the cylindricalmantle 11 of the cyclone separator 10 as the flow a, whose direction, asit revolves around the centre pipe 13, is downwards. When the revolvingflow a reaches the conical bottom portion 14 of the cyclone separator10, the flow a starts revolving with an ever shorter radius of rotation,while the flow a, nevertheless, still corresponds to the velocity of theincoming flow A. This is why, in the conical bottom portion 14, theangular velocity of the flow a becomes ever higher and higher. Then, thecentrifugal force/field increases in proportion to the second power ofthe angular velocity, and this is why, in the increasing centrifugalfield, the particles of solid matter are cast onto the walls of theconical lower portion 14, from where they sink into the outlet openingof the conical bottom portion 14 and through said opening into theclosing part 15 in itself known, from which they can be removed as theflow B. At the lower end of the conical bottom portion 14, the flow a isconverted to a flow b that is directed upwards, i.e. to a so-calledtornado flow, which has the same sense of rotation as that of the flowa, but whose direction is towards the lower orifice of the centre pipe13. The tornado flow b penetrates into the interior of the flow a ofopposite principal flow direction, because of the conical shape of theconical lower portion 14. As the flow velocity continues to besubstantially the same as the flow velocity of the incoming medium flowA, the angular velocity of the tornado flow b becomes multiple ascompared with the angular velocity of the flow a. This results in theformation of an intensive vacuum inside the tornado flow b and in itsclose vicinity.

According to the invention, inside the centre pipe 13 of the cycloneseparator 10, preferably on the central axis of the centre pipe, thecomponent-flow pipe 16 is placed, whose diameter is considerably smallerthan the diameter of the centre pipe 13. The open lower end of thecomponent-flow pipe 16 is directed directly towards the tornado flow bthat was formed in the conical bottom portion 14. The component-flowpipe 16 extends preferably beyond the orifice of the centre pipe 13towards the conical bottom portion 14 in order that the vacuum effectproduced by the tornado flow b should become sufficiently intensive toproduce the component flow c, preferably out of the medium flow Aflowing into the cyclone separator 10.

The top end of the component-flow pipe 16 preferably extends to thevicinity of the top end of the centre pipe 13, where it passes throughthe wall of the centre pipe 13. The component flow c entering from thereinto the component-flow pipe 16 can disintegrate the tornado flow b andthe solid matter contained in same as the component flow c is dischargedfrom the bottom end of the component-flow pipe 16. Thus, the solidmatter contained in the tornado flow b is dispersed among the flow a,being thereby recirculated to separation.

When the component flow c is taken from the medium flow A entering intothe cyclone separator 10, its magnitude in comparison to the medium flowA is negligible, as a rule, less than 10 percent by volume, preferably0.1 . . . 5 percent by volume. Thus, this component flow c takes placeentirely by itself inside the cyclone separator 10. Such a componentflow c requires a difference in pressure of 200 . . . 500 Pa, which isalready produced also in low-pressure cyclones when the cyclone receivesits nominal flow A. Of course, the flow entering into the component-flowpipe 16 is already partly produced out of the difference in pressure,arising from the pressure loss of the cyclone, present at the orifice ofthe centre pipe 13 as compared with the pressure present at the inletopening 12 of the cyclone. Having disintegrated the tornado flow b, thecomponent flow c discharged out of the component-flow pipe 16 entersinto the flow a revolving inside the cyclone.

By means of the method in accordance with the invention, a very highincrease in the efficiency of separation is achieved, as compared withthe efficiency of separation of a conventional cyclone. By means of theinvention, it is possible to eliminate the tornado effect completely,which effect is present in every cyclone when it is in operation. On theother hand, the effect of the solution in accordance with the inventionon the construction, cost of manufacture, and on the appearance of thecyclone separator remains fully negligible.

The location of the lower end of the component-flow pipe 16 in theconical bottom portion 14 depends, among other things, on the steepnessof the conical lower portion 14 and on the velocity of the flow a, i.e.on the loading of the cyclone.

Generally speaking, the initial end of the conical lower portion 14 canbe considered to be a preferable location of the lower end of thecomponent-flow pipe 16, but the invention is by no means critical inrespect of the precise location of the lower end of the component-flowpipe 16. It is the principal objective of the invention that thecomponent flow c entering into the component-flow pipe 16 should be, asprecisely as possible, equal to the amount that is required for completedisintegration of the tornado flow b formed in the cyclone separator 10.This must, of course, be found out and measured for each cycloneconstruction separately. Owing to the invention, the medium flowcleansed by the cyclone separator 10 can be made to escape into thecentre pipe 13 as cleansed from the solid matter contained in thetornado flow b. In such a case, the cleansed medium flow C departingfrom the centre pipe 13 of the cyclone 10 is as clean as possible.

Above, the solution of principle of the invention has been describedonly, and it is obvious for a person skilled in the art that numerousmodifications can be made to said solution within the scope of theinventive idea defined in the accompanying claims.

I claim:
 1. In a cyclone separator intended for separating and cleansinga gaseous medium flow and including a substantially cylindrical upperpart having an inlet duct through which the gaseous medium flow to becleansed flows as a incoming medium flow into an interior of the cycloneseparator, a conical lower part, and a center pipe through whichcleansed gaseous medium is removed as an outlet flow from the interiorof the cyclone separator, the improvement comprising:a component-flowpipe having an inlet opening arranged in a wall of the center pipe andan outlet end arranged opposite the lower portion of the conical lowerpart such that the component-flow pipe extends through an interior ofthe center pipe, a component flow portion of the incoming medium flowbeing passed from a location exterior of the center pipe and within theinterior of the cyclone separator through the wall of the center pipeinto the component-flow pipe and from the component-flow pipe against atornado flow formed in the lower portion of the conical lower part suchthat the component flow disintegrates the tornado flow and preventssolid matter from being carried through the center pipe with the outletflow of the cleansed gaseous medium.
 2. In a method for improving theseparation and cleansing efficiency of a cyclone separator intended fora gaseous medium flow in which the gaseous medium flow to be cleansedflows as a incoming medium flow into an interior of the cycloneseparator through an inlet duct and flows in a revolving flow movementinside a substantially cylindrical upper part of the cyclone separatorand an upper portion of a conical lower part of the cyclone separator,the revolving flow movement of the gaseous medium flow being changed ina lower portion of the conical lower part of the cyclone separator intoa revolving tornado flow movement in an opposite direction to thedirection of the revolving flow movement in the upper portion of theconical lower part of the cyclone separator, solid matter beingseparated from the gaseous medium in the cyclone separator whereby thegaseous medium from which solid matter is separated is directed from thecyclone separator through a center pipe, the improvement comprising thesteps of:arranging a component-flow pipe to extend at least from anopening in a wall of the center pipe to a location within the centerpipe, passing a component flow portion of the incoming medium flow froma location exterior of the center pipe and within the interior of thecyclone separator into the component-flow pipe, and directing thecomponent flow from the component-flow pipe against the tornado flowsuch that the component flow disintegrates the tornado flow and preventssolid matter from being carried through the center pipe into an outletflow of the cleansed gaseous medium.
 3. The method of claim 2, furthercomprising the step of controlling the amount of the component flowbeing separated from the incoming medium flow such that the amount ofthe separated component flow is less than about 10 percent by volume ofthe incoming medium flow.
 4. The method of claim 2, further comprisingthe step of controlling the amount of the component flow being separatedfrom the incoming medium flow such that the amount of the separatedcomponent flow is from about 0.1 to about 5 percent by volume of theincoming medium flow.
 5. The method of claim 2, further comprising thestep of positioning the location of a lower end of the component-flowpipe relative to the lower portion of the conical lower part such thatthe tornado flow has sufficient space to develop.
 6. The method of claim2, wherein the component-flow pipe has a diameter which is smaller thanthe diameter of the center pipe.
 7. The method of claim 2, wherein thestep of passing the component flow into the component-flow pipecomprises the step of forming a vacuum as a result of the tornado flowin the lower portion of the conical lower part of the cyclone separatorsuch that a difference is pressure is created between an outlet end ofthe component-flow pipe proximate to the lower portion of the conicallower part of the cyclone separator and an inlet end of thecomponent-flow pipe through which the component flow is passed from theincoming medium flow.
 8. The method of claim 2, further comprising thestep of positioning the component-flow pipe such that a central axis ofa cylindrical portion of the component-flow pipe is coincident with acentral axis of the center pipe.
 9. The method of claim 2, wherein thecomponent-flow pipe is arranged to extend from a location exterior ofthe center pipe and within the interior of the cyclone separator througha side wall of the center pipe to the interior of the center pipe. 10.The method of claim 2, wherein the component flow is separated from theincoming medium flow at a location within the substantially cylindricalupper part of the cyclone separator.
 11. A method for separating andcleansing a gaseous medium in a cyclone separator, comprising the stepsof:directing the gaseous medium to be cleansed as a incoming medium flowinto an interior of the cyclone separator through an inlet duct to causethe incoming medium flow to flow in a revolving flow movement inside asubstantially cylindrical upper part of the cyclone separator and anupper portion of a conical lower part of the cyclone separator, therevolving flow movement of the incoming medium flow being changed in alower portion of the conical lower part of the cyclone separator into arevolving tornado flow movement in an opposite direction to thedirection of the revolving flow movement in the upper portion of theconical lower part of the cyclone separator, directing cleansed gaseousmedium from which solid matter has been separated in the cycloneseparator from the cyclone separator through a center pipe extendingthrough the cylindrical upper part of the cyclone separator, arranging acomponent-flow pipe to extend at least from an opening in a wall of thecenter pipe to a location within the center pipe, and passing acomponent flow portion of the incoming medium flow from a locationexterior of the center pipe and within the interior of the cycloneseparator into the component-flow pipe, and directing the component flowfrom the component-flow pipe against the tornado flow such that thecomponent flow disintegrates the tornado flow and prevents solid matterfrom being carried through the center pipe into an outlet flow of thecleansed gaseous medium.
 12. The method of claim 11, wherein thecomponent-flow pipe is arranged to extend from a location exterior ofthe center pipe and within the interior of the cyclone separator througha side wall of the center pipe to the interior of the center pipe andthe component flow is separated from the incoming medium flow at alocation within the substantially cylindrical upper part of the cycloneseparator.
 13. A method for improving the separation efficiency of acyclone separator intended for gaseous medium flows, comprising thesteps of:directing an incoming gaseous medium flow to be cleansed intothe cyclone separator through an inlet duct such that the incomingmedium flow ends up in a downward, revolving flow movement inside thecyclone separator until the incoming medium flow reaches a bottom end ofa conical lower part of the cyclone separator and then becomes arevolving tornado flow that flows in a generally upward directionopposite to the direction of the downward, revolving flow movement,directing an outlet flow of cleansed gaseous medium through a centerpipe situated in the cyclone separator, arranging a component-flow pipein the center pipe such that the component-flow pipe has an inletopening in a wall of the center pipe, passing a component flow of theincoming medium flow from a location within the cyclone separatorthrough the inlet opening in the wall of the center pipe into thecomponent-flow pipe, and directing the component flow out of thecomponent-flow pipe against the tornado flow that has been formed suchthat the component flow disintegrates the tornado flow and therebyprevents solid matter from being carried along with the tornado flowthrough the center pipe into the outlet flow of the cleansed mediumflow.
 14. A method as claimed in claim 13, further comprising the stepof utilizing as the component flow, a flow that is less than 10 per centby volume of the incoming medium flow.
 15. A method as claimed in claim13, further comprising the step of utilizing as the component flow, aflow is used that is from 0.1 to 5 percent by volume of the incomingmedium flow.
 16. A method as claimed in claim 13, further comprising thestep of positioning the location of the lower end of the component-flowpipe such that the tornado flow has time to be formed completely.
 17. Amethod as claimed in claim 13, further comprising the step of utilizingas the component-flow pipe, a pipe whose diameter is smaller than thediameter of the center pipe.